FACTORS IN ONTOGENY 



C 



FIG. 157. A, Hybrid larva (Sphcerechinus 9 and Echinus &}, front view; B, the same 

 from side view; C, hybrid larva, Sphcerechinus $ (nonnucleated egg formation,) 

 and Echinus i , of the type; D, the same larva in side view. (After Boveri.) 



19 



